: The proposed project will investigate the biological mechanisms that are hypothesized to underlie socioeconomic differences in health outcomes among older people. While the fact that poorer and less educated people have higher rates of death Abstract): The proposed project will investigate the biological mechanisms that are hypothesized to underlie socioeconomic differences in health outcomes among older people. While the fact that poorer and less educated people have higher rates of death, disease, and disability has been widely documented, the question of what biological mechanisms give rise to these socioeconomic differences remain largely unspecified. The proposed analyses will use data on a wide range of biological parameters to examine their role, both individually and cumulatively, in explaining socioeconomic differences in four major health outcomes: death, myocardial infarction, change in physical functioning, and change in cognitive function. The project will use data from the MacArthur Study of Successful Aging, a longitudinal study of 1189 socioeconomically-divers persons aged 70-79 years at baseline, who were interviewed three times during the 1988 to 1996 period. At the time of each interview, sample members provided information about current health conditions and were given a series of performance tests to measure aspects of their physical and cognitive function. Survey information on health outcomes will be augmented with information from Medicare records and the National death Index. Indicators of biological mechanisms are derived from standard medical tests performed at interview and assays of blood and urine samples provided by sample members. The socioeconomic diversity and the range of biological information available in this data set make it ideal for the proposed project. Knowledge of the role of biological risk profiles in producing differential health outcomes by socioeconomic status will provide important information to assist in targeting health care and education resources to reduce health differentials.